In general it is quite bad form to touch the user's stack at all forinstrumentation purposes. Unexpected stack usage might be what you aretrying to debug, after all.

On x86-64 in particular, it is strictly verboten to touch the user's stackimmediately below the SP. In the x86-64 ABI, the 128 bytes below %rsp area scratch area for leaf functions that normal compiled user code will useto store data that must not be clobbered. (Normal signal handler framesstart 128 bytes below %rsp for this reason.)

That's aside from the more obvious issues Josh mentioned, where theinstruction itself is a push/pop/call/ret or uses an addressing moderelative to %rsp.